Add progress events for loading DDC summaries to make it clear to users whether loading a DDC appli…

pkg/dev_compiler/web/main.dart

Index: pkg/dev_compiler/web/main.dart
diff --git a/pkg/dev_compiler/web/main.dart b/pkg/dev_compiler/web/main.dart
index b7cdea65f64bac591edcbcc4d416bb86db60c930..af28187835f00d632e4a6860834ecb66cdfdc63e 100755
--- a/pkg/dev_compiler/web/main.dart
+++ b/pkg/dev_compiler/web/main.dart
@@ -26,9 +26,10 @@ main() {
   setUpCompilerInBrowser = allowInterop((String sdkUrl,
       JSMap<String, String> summaryMap,
       Function onCompileReady,
-      Function onError) async {
+      Function onError,
+      [Function onProgress]) async {
     (await _setUpCompilerInBrowser)(
-        sdkUrl, summaryMap, onCompileReady, onError);
+        sdkUrl, summaryMap, onCompileReady, onError, onProgress);
   });
   _runCommand(args);
 }